Less, I have been using an old version of PrimoPDF without any problems since 2004, in both a 98SE and XP PC. My requirements are very simple (occasional PDF) and never needed to upgrade. I see that the new version 4 has more bells and whistles. Perhaps you want to try it and post back your opinion.

There's another program, PDFTK Builder Portable, that also fits your requirements and although I have it on an USB drive, I've never played with it. You're more than welcome to try it too.